Background

Thiamine (vitamin B1) is found in many foods and is used to treat low thiamine, beriberi, certain nerve diseases, and Wernicke-Korsakoff syndrome (WKS).

Thiamine is required by our bodies to properly use carbohydrates. It also helps maintain proper nerve function. It's found in foods such as yeast, cereal grains, beans, nuts, and meat. It's often used in combination with other B vitamins, and is found in many vitamin B complex products.

People take thiamine for conditions related to low levels of thiamine, including beriberi and inflammation of the nerves (neuritis). It's also used for digestive problems, diabetic nerve pain, heart disease, and other conditions, but there is no good scientific evidence to support these other uses.

Safety Safety definitions

When taken by mouth: Thiamine is commonly consumed in the diet and is likely safe when taken in appropriate amounts.

Special Precautions & Warnings:

Pregnancy and breast-feeding: Thiamine is likely safe when taken by mouth as part of the diet. There isn't enough reliable information to know if higher doses are safe to use when pregnant and breast-feeding.

Children: Thiamine is likely safe when taken by mouth as part of the diet. There isn't enough reliable information to know if higher doses are safe or what the side effects might be.

Alcohol use disorder: People with alcohol use disorder often have low levels of thiamine and might need thiamine supplements. Nerve pain from alcohol use disorder can be worsened when thiamine levels are low.

Hemodialysis: People undergoing hemodialysis treatments might have low levels of thiamine and might need thiamine supplements.

Liver disease: People with chronic liver disease often have low levels of thiamine and might need thiamine supplements.

Effectiveness

Dosing & administration

Thiamine is an important nutrient. It's found in many foods, including cereal grains, beans, nuts, and meat.

The amount that should be consumed on a daily basis is called the recommended dietary allowance (RDA). For adult males, the RDA is 1.2 mg daily. For adult females 18 years of age, the RDA is 1 mg daily. For adult females 19 years and older, the RDA is 1.1 mg daily. The RDA during pregnancy and breastfeeding is 1.4 mg daily. Recommended amounts for children depend on age. Speak with a healthcare provider to find out what dose might be best for a specific condition.

Interactions with pharmaceuticals

Trimethoprim (Proloprim)

Interaction Rating=Minor Be watchful with this combination.

Thiamine is moved in and out of cells by pumps. Trimethoprim might change how these pumps work and increase how much thiamine stays in the body. In some cases, this might change the effects and side effects of thiamine.

Interactions with herbs & supplements

Betel Nut: Betel nuts change thiamine so it doesn't work as well. Regular, long-term chewing of betel nuts may contribute to thiamine deficiency.
Horsetail: Horsetail contains a chemical that can destroy thiamine in the stomach, possibly leading to thiamine deficiency. The Canadian government requires that horse chestnut products be certified as free of this chemical. Stay on the safe side, and don't use horsetail if you are at risk for thiamine deficiency.

Interactions with foods

Eating certain foods might reduce how much thiamine the body can absorb, which could lead to thiamine deficiency. Tannin-containing foods and beverages, such as coffee and tea, might have this effect. But you would need to consume a very large amount every day to cause deficiency. People who consume normal amounts of thiamine and vitamin C in the diet should not have this issue.

Eating a lot of raw fish or shellfish can also contribute to thiamine deficiency. But cooked fish and seafood aren't a problem. They don't have any effect on thiamine, since cooking destroys the chemicals that harm thiamine.